Blood in your stool is usually caused by something minor and treatable. In about 90% of cases seen in primary care, rectal bleeding traces back to a self-limiting condition like hemorrhoids or a small tear in the skin around the anus. That said, the color, amount, and accompanying symptoms all matter, and roughly 3% of patients with rectal bleeding are eventually diagnosed with colorectal cancer. Understanding what different types of bloody stool look like can help you figure out how urgently you need to act.
What the Color of the Blood Tells You
The shade of blood you see is a useful clue about where the bleeding originates. Bright red blood typically comes from the lower part of your digestive tract, meaning the rectum or colon. You might notice it on the toilet paper, dripping into the bowl, or coating the surface of your stool. This is the most common type of rectal bleeding and is often linked to conditions close to the exit point.
Dark, tarry, almost black stool points to bleeding much higher up in the digestive tract, such as the stomach or upper small intestine. Blood that travels that far gets partially digested along the way, which turns it dark and gives the stool a sticky, tar-like consistency with a distinctly foul smell. This type of bleeding is less common but generally more concerning and warrants prompt medical attention.
Foods That Mimic Bloody Stool
Before assuming the worst, consider what you ate in the last day or two. Several foods can turn your stool red, pink, or maroon without any bleeding involved. Beets are the most well-known culprit. The pigment that gives beets their deep ruby color can pass through your digestive system and tint your stool pink to maroon. Cranberries and blueberries can do the same.
Tomatoes and watermelon are both high in lycopene, a red pigment that can color your stool if you eat enough of them. A big bowl of tomato soup or a plate of fresh salsa may be all it takes. You might also spot fragments of red pepper or tomato skin in the toilet, which look alarming but are just undigested vegetable fiber. Red food dye, especially Red 40 (found in candy, sugary cereals, chips, and gelatin desserts), is another frequent cause of false alarms.
Hemorrhoids and Anal Fissures
These two conditions are by far the most common reasons for bright red blood in your stool, and they feel quite different from each other.
Hemorrhoids are swollen blood vessels in or around the rectum. About half of all people will have one by age 50. Most hemorrhoids don’t actually cause pain. You might notice painless bright red blood on the tissue or in the bowl, along with itching or a feeling of fullness near the anus. Internal hemorrhoids, which sit inside the rectum, are especially likely to bleed without hurting.
Anal fissures are small tears in the skin lining the anal canal, and they tend to hurt considerably more. The hallmark is a sharp or burning pain during a bowel movement that can linger afterward. Fissures are most common in infants and adults over 50, and they often develop after passing a hard or unusually large stool. Both conditions can usually be diagnosed with a simple physical exam.
Infections That Cause Bloody Diarrhea
If blood in your stool comes alongside fever, cramping, and watery or mucus-filled diarrhea, a bacterial or parasitic infection is a likely cause. Several common foodborne pathogens can inflame the lining of the colon enough to cause bleeding. These include certain strains of E. coli, Salmonella, Shigella, and Campylobacter. A parasitic infection called amoebic colitis can produce similar symptoms.
These infections typically develop within a few days of eating contaminated food or water and often resolve on their own within a week. The combination of bloody diarrhea with a fever is the pattern that most strongly suggests an infectious cause rather than a structural one like hemorrhoids.
Inflammatory Bowel Disease
Crohn’s disease and ulcerative colitis are chronic conditions where the immune system attacks the lining of the digestive tract, causing ongoing inflammation. Both can produce rectal bleeding, but they come with a broader set of symptoms that distinguish them from simpler causes: persistent diarrhea, abdominal pain or cramping, unintended weight loss, fatigue that doesn’t improve with rest, loss of appetite, mouth ulcers, and sometimes fever.
These symptoms tend to follow a pattern of flare-ups and remission rather than appearing once and disappearing. If you’re experiencing bloody stool along with several of these other symptoms, especially over weeks or months, inflammatory bowel disease is something your doctor will want to investigate.
Colorectal Cancer
This is the possibility most people are searching about when they look up bloody stool, and the statistics are reassuring: only about 3% of patients who present to a doctor with rectal bleeding turn out to have colorectal cancer. Still, it’s a cause worth knowing about. Colorectal cancer can produce either bright red blood or darker blood mixed into the stool, sometimes in amounts too small to see with the naked eye.
The U.S. Preventive Services Task Force recommends that all adults begin screening for colorectal cancer at age 45. For people at average risk, a colonoscopy every 10 years or a stool-based test (like a fecal immunochemical test) every year are among the standard options. If you’re under 45 and have no family history or other risk factors, a single episode of bright red rectal bleeding is far more likely to be hemorrhoids than cancer. But persistent bleeding, unexplained weight loss, or a change in bowel habits that lasts more than a few weeks deserves evaluation regardless of your age.
What Happens at the Doctor’s Office
Evaluating rectal bleeding usually starts simply. Your doctor will ask about the color and frequency of the blood, your bowel habits, diet, and any other symptoms. A physical exam typically includes an abdominal exam and a digital rectal exam, where the doctor uses a gloved finger to feel for hemorrhoids, fissures, or masses near the rectum. Blood work, including a complete blood count, can reveal whether you’ve lost enough blood to become anemic.
If the cause isn’t obvious from the exam, the next step is usually a colonoscopy, where a flexible camera examines the entire length of the colon. During the procedure, your doctor can take tissue samples or remove polyps on the spot. For urgent cases, specialists typically aim to complete this workup within two to four weeks of referral. Less urgent cases may take up to eight weeks. If a standard colonoscopy can’t fully examine the colon, a CT scan of the colon (virtual colonoscopy) may be used instead.
Signs That Need Emergency Attention
Most rectal bleeding can wait for a scheduled appointment, but certain combinations of symptoms signal a medical emergency. Call 911 or get to an emergency room if rectal bleeding is continuous or heavy, or if it comes with severe abdominal pain or cramping.
You should also seek emergency care if you notice signs that your body isn’t coping with the blood loss: rapid, shallow breathing, dizziness or lightheadedness when you stand up, blurred vision, fainting, confusion, nausea, cold or clammy skin, or very little urine output. These are signs of shock, meaning your circulatory system is struggling, and they require immediate treatment.